The present invention relates to detachable coupling for bicycle transmissions and, more particularly, to an easily detachable coupling for connecting a pull cable to an internal gear hub.
A detachable coupling allows the cable pull to be connected or disconnected from the gear hub before connecting or disconnecting the driving wheel. A detachable coupling is disclosed in European Patent Application EP 0805104A2 that includes a casing for housing a control cable that is connected to a rear wheel multispeed hub having a driving wheel. The driving wheel is positioned, coaxially to the hub axle, at one of the ends of the hub. The cable spool converts the linear movement of the control cable into a rotating movement. The casing includes a drive casing for covering the driving wheel and a casing extension for accommodating the control cable and the cable. A joint having a cable guide connects the drive casing to the casing extension. The casing extension is tubular and has an opening covered by a hinged lid and a fastening element to attached it to the bicycle frame. A spring element and a coupling is accommodated in the casing extension. The operating pull is connected to one end of the spring element by a clamp and the cable is connected to the other end of the spring element. A cable casing supports itself on an adjusting screw connected to the casing extension.
To disconnect the connecting device, the shifting position is set to position resulting in the least amount of cable pull tension. The hinged lid on the casing extension is swung open and spring element and the coupling are removed from the casing extension and then separated from one another. The spring element remains on the casing extension, and consequently on the driving wheel, while the cable casing with the adjusting screw and the cable with the coupling piece remain on the bicycle frame.
Another connecting device is disclosed in U.S. Pat. No. 6,349,614. Here, the casing adjacent the hub leads into a tube extension to guide the shifter cable and to house one end of the cable casing. The other end of the cable casing is accommodated by a clamping device, which provides the necessary installation space for the connecting device of the shifting and pull cables and supports the cable casing of the pull cable connected to the shift actuator.
The connection between the shifting cable and the pull cable is a detachable screw or bayonet connection. The corresponding parts of the bayonet connection are connected to the ends of the shifting or pull cable. To detach the connecting device, the shift adjustment is set to the least pull cable tension and the screw or the bayonet connection is opened by twisting the corresponding components. Locking parts are located within an open holding device, resulting in the locking parts being unprotected. Since the locking parts are unprotected, it is necessary to seal the cables during the shifting process and the locking parts. The cable pull with the appropriate locking part and the cable casing may be removed from the slotted receptacle in the holding device. When the driving wheel is detached, the casing remains with the shifter cable and the cable casing with the holding device on the wheel, while the cable pull remains with its cable casing on the bicycle frame.
The problem with the above devices is that in order to connect or disconnect the pull cable from the shifting cable, the cable connection must either be removed with difficulty from the casing extension or twisted against each other in the holding device. The connecting device with the casing extension requires relatively a lot of installation space and is difficult to handle if a wheel needs to be changed since the hinged lid must be opened and the cable connection removed and unhooked for releasing. The connecting device with the open holding device is very dirt-prone since it is right next to the chain, and despite the open holding device, the twisting of the bayonet connection is prevented. Even there, the handling of the detached wheel is impaired by the shifter cable or shifter cable casing that remains sticking out on the hub.